CAMBRIDGE, Mass. & SIENA, Italy--(BUSINESS WIRE)--Elixir Pharmaceuticals, Inc. and Siena Biotech S.p.A. announced today that the two companies have entered into an agreement to collaborate on the optimization, validation and evaluation of Elixir’s SIRT1 inhibitors in Huntington’s disease. Huntington’s disease is a hereditary, degenerative brain disorder for which there is no present effective treatment or cure.